Child vs. Adult Onset of Attention-Deficit/Hyperactivity Disorder

To the Editor: Two longitudinal studies of epidemiological cohorts published in JAMA Psychiatry—one conducted in Brazil1 and the other in the United Kingdom2—have found evidence for adult-onset attention-deficit/hyperactivity disorder(ADHD) in substantial proportions of adults with ADHD. These studies, plus an earlier one from NewZealand,3 challenge the longstanding conceptualization of ADHD as a disorder necessarily beginning in childhood. The strengths of these studies include large sample sizes and longitudinal prospective birth cohort designs. Thus, the childhood diagnostic data were collected in childhood and not dependent on retrospective (and possibly biased) reports.

Nevertheless, I submit that these unexpected results may reflect the method used to diagnose the disorder in children. Specifically, the DSM-III ADHD diagnostic criteria in use at the time of initiation of the New Zealand study did not allow for diagnosis of the inattentive subtype or presentation of ADHD, whichcomprises45%4 of all children with ADHD. Children with the inattentive subtype would similarly not have been recognized in the Brazil study,1 which used the 5-item hyperactivity subscale of the Strengths and Difficulties Questionnaire to screen the participants. Exclusion of predominantly inattentive cases would result in a significantly reduced occurrence of childhood ADHD among the Adults with ADHD. Children in the UK study2 were diagnosed as having the disorder on the basis of the full DSM-IV criteria for ADHD, which recognized the subtypes, which may explain why it reports a much higher percentage of adults with ADHD having onset in childhood (32.5%) than did the New Zealand study (10%) or the Brazil study (12.6%).

I see 100 adults per year for evaluation and/or treatment of ADHD, most of whom have clear onset of symptoms in childhood, with an additional number reporting onset in adolescence. Thus, I believe it would be premature to implement a diagnosis of an “adult-onset ADHD” without understanding more fully why clinical samples differ from the epidemiological samples reported in these studies.